Steel sheets used for manufacturing bodies-in-white for the automobile industry are generally coated with a zinc-based metal layer for corrosion protection, deposited either by hot-dip coating in a zinc-based liquid bath or by electro-deposition in an electroplating bath containing zinc ions.
In the continuous galvanizing process, known as hot-dip galvanizing process, the continuously moving metal strip is dipped into a bath of molten metal. It is then dragged out of the bath, and a turbulent slot jet is used to wipe the excess metal and control the thickness of the coating.
DE 40 10 801 discloses an installation for hot dip coating a metal strip comprising a pot containing a melt bath and a wiping system for wiping the coated metal strip after it exits the melt bath. The wiping system comprises a confinement box having an upper confinement part which is fixed relative to the pot, and a lower confinement part which can be displaced vertically relative to the pot and to the upper confinement part between a bottom position in which it is partially immersed in the melt bath and a top position in which there exists a free space between the bottom edge of the confinement box and the surface of the melt bath.
Such an installation is not entirely satisfactory. Indeed, the quality of the coating will vary e.g. depending on operating parameters of the line, such as the speed of the line or the wiping pressure, as well as on the format of the metal strip, such as its width or thickness. Therefore, the installation disclosed in DE 40 10 801 cannot be used to achieve satisfactory coatings for all kinds of productions.